(626h) Media Optimization for Enhanced Propionic Acid Production by Propionibacterium Acidipropionici

Propionic acid is consumed as human food and animal feed preservatives due to its inhibition effect on the growth of mold and some bacteria. Besides petroleum-based chemical synthesis, an alternative way to produce propionic acid is through fermentation, which is safe, sustainable and environmentally benign. Propionibacterium acidipropionici has been the most used species for propionic acid production from sugars. In this study, we compared various carbon sources (glucose, fructose and sucrose) and found no significant differences in propionic acid production. Furthermore, industrial grade substrate and nutrients as sugarcane juice or molasses were used as basal media to lower the feedstock cost. Yields (0.5g/g glucose) are comparable for both sugarcane juice and synthetic medium. Different nitrogen sources were added to the basal media to improve the production of propionic acid. NH₃, ammonium chloride, ammonium sulfate were good candidates for inorganic nitrogen sources, while corn steep liquor (CSL), yeast, yeast extract, for organic nitrogen sources. Minerals and vitamins as Ca-pantothenate, thiamine, biotin were tested to enhance the propionic acid final titer and yield.   Salt effect (KCl,  NaCl) and propanol inhibition were also studied:  0-80g/L NaCl or 0-100g/L KCl) significantly inhibited cell growth and propionic acid production; and when the propanol in the media is over 25g/L, the inhibition effect became significant.